Single-frequency subsurface remote sensing via a non-cooperative source

The problem of detecting buried scatterers from their scattered field collected under a remote arrangement (i.e. with the sensors deployed at some stand-off distance from the air/soil interface) is considered. A new imaging method that does not require the knowledge of the incident field, information about the transmitting antenna position or timing is proposed. More in detail, the detection problem is cast as the reconstruction of the support of the equivalent surface currents (located at the air/soil interface), which the scattered field can be ascribed to. To this end, a single-view/multistatic configuration, which also reduces the radar system’s cost and complexity, can be employed. It is remarked that the proposed method does not allow to retrieve the scatterers’ depth. Therefore, it is conceived for all those situations where depth is of minor importance or when it is a priori known that the scatterers reside just beneath to the air/soil interface. This is the case, for example, in mine or unexploded improvised device detection where the primary aim is to detect the buried ordnances and locate them transversally. In these cases, the need for a frequency band can be relaxed as well, so that reconstructions can be achieved also in the single-frequency limit case. The latter is clearly a further advantage in that it simplifies the imaging system. The proposed method is checked against half-space synthetic data. The paper also includes some experimental results with data collected under free-space controlled laboratory conditions that can be considered as a proof of concept.